Method of and apparatus for supplying carbon dioxide gas



c. L. JONES 1,951,758

METHOD OF AND APPARATUS FOR SUPPLYING CARBON DIOXIDE GAS March 20, 1934.

Filed April 15, 1930 INVENTOR Patented Mar. 20, 1934- UNITED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR SUPPLY- ING CARBON DIOXIDE GAS 10 Claims.

The present invention is concerned with a method of and apparatus forsupplying carbon dioxide gas. While capable of a wide range of utility in supplying carbon dioxide gas for various industrial purposes, it is peculiarly adapted for supplying carbon dioxide gas for oil immersed electrical apparatus, such, for instance, as transformers, regulators or circuit breakers.

The desirability of maintaining an inert at- -mosphere of carbon dioxide over the oil bath in this type of apparatus is well recognized, such inert atmosphere being particularly effective to prevent oxidation of the oil and to lessen the hazard of fire or explosions within the apparatus. Temperature increases to which the oil and gas contents of such apparatus are subjected raise the oil level, expand the gas, and result in an outbreathing of the gas content of the apparatus through gas leaks in the casing. Subsequent inbreathing as the temperature falls, results in sucking in air and contamination or dilution of the inert gas layer which should be maintained upon the oil. In my prior Patent No. 1,641,814, granted September 6, 1927, I provide a method and apparatus which assures the maintenance of an uncontaminated body of carbon dioxide in the top of a transformer by supplying the gas from an ordinary steel cylinder in which it is stored under very high pressure, by continuous regulated discharge through an adjustable valve.

The bottom of the casing is connected through a valve controlled pipe to the tank of compressed carbon dioxide gas. The excess gas escapes through a tortuous breather outlet leading from the top of the transformer casing. Under normal operating conditions, this permits a slow and continuous leak of compressed carbon dioxide gas into the transformer. This gas bubbles up through the oil and forces a normally continuous out-breathing of the heavier-than-air gas through said outlet from the transformer casing, against the pressure developed by the weight and inertia of a gas column in the tortuous breather outlet.

Constantly venting gas prevents sucking in of air, even when a wide temperature drop occurs in the transformer due to weather conditions or the cessation of electrical current in the transformer.

I have found the patented apparatus and method to be as eflicient for most purposes as any apparatus involving a mechanical metering valve can be. However, absolutely dependable operation over long periods of time without attendance is a prime desideratum and this cannot be obtained with valve mechanism, because there is always the possibility of a valve, however well designed, becoming stuck or clogged or changed in adjustment.

The desired continuous and dependable operation is accomplished by my present invention in which all valves are eliminated and the gas supply chamber communicates directly with the transformer through a small but unrestricted 65 passageway.

Compressed gas from an ordinary source, such as a tank, cannot be controllably passed through a conduit to the transformer except when controlling valves are used. The usual'gas generating systems are impracticable for the purpose, their control being accomplished only with difficulty.

I propose, therefore, in the present case, to use frozen carbon dioxide as a gas generating source, '(5 maintaining it in a heavily insulated gas-tight chamber and controlling the fiow of gas through a valveless passage to the transformer by regulating the temperature of the chamber. This temperature regulation may be effected from a thermostat, barometer, gas-analyzer or other suitable controller at the point of use of the gas.

In considering the efiectiveness of the proposed arrangement it will be borne in mind that there are no high pressures to contend with since the ice will be melted at a pressure preferably well below its triple point of 5.11 atmospheres. A block of carbon dioxide ice of ordinary density will yield approximately 500 times its volume in gas and the snow proportionally, according to its density. With the ice chamber effectively insulated and thermal equilibrium once established, the consumption of the ice or snow will be extremely small and a small charge of ice or snow will serve to maintain proper inert gas conditions in a relatively large transformer over a long period of time.

In accordance with a preferred embodiment of the invention, the chamber containing the frozen carbon dioxide is insulated heavily enough to reduce the sublimation rate down to near or below the minimum gas requirements of the apparatus and any desired higher rate of gas generation or ice sublimation is caused and controlled by a small heat-generating resistance coil in the ice chamber, current flow through the resistance being regulated in any suitable manner from the region at which the gas is being used.

Another feature of the apparatus is the provision of a special ice receptacle which not only provides for effective ice insulation but which may be readily charged with ice and which may be equipped with a simple form of liquid seal to prevent gas leaks, it being remembered that pressures in the ice chamber are always low.

The invention may be more fully understood from the following description in connection with the accompanying drawing, wherein- Figure 1 is a diagrammatic view showing a complete system for controllably supplying inert gas to a transformer;

Figure 2 is an enlarged transverse sectional view of the ice box.

The receiver for the frozen carbon dioxide may consist of an outer container orv box 10 equipped with a removable cover 11. The box walls, as well as the cover, are heat insulated. They may be hollow as shown and filled with cork 10 or some equivalent insulating material or they may be hollow and vacuumized in the well-known manner.

Preferably, the cover 11 is provided with a peripheral radial'flange 12 from which depend any suitable number of concentric partition members 13 adapted to articulate with upstanding partition members 14 on the box body and cooperatively define therewith a labyrinthine passageway adapted to be filled with oil or any other suitable liquid to-form a liquid seal and prevent escape of gas. The inner container 15, for the frozen carbon dioxide, is preferably of metal and permits escape of the gas only by outflow from the top thereof. Between the inner and outer containers and spaced therefrom is a partition 16, preferably pendent from the cover so as to be removable therewith. This affords a down and up path of escape for the gas, in the interspaces, from the inner container 15 to the outlet 17. The layers of dry gas afford very high insulation and as the layers flow countercurrent, one outside the other, they also act to carry in-leaking sensible heat backward toward the exterior.

In case more than the two layers of dry gas as shown in the drawing are desired, the desired number of insulating layers of the out-flowing gas may be secured by providing the cover with a plurality of downwardly extending partitions like the partition 16, and by providing in the space between the inner container 15 and the outer container 10 .with similar partitions extending upwardly between the partitions which project downwardly from the cover, so as to provide a tortuous up and down path for the gas between the partitions.

The outlet 17 from the ice container communicates with a relatively restricted conduit 18 leading directly into the casing 19 of a transformer or equivalent apparatus. Preferably, the ice container is located below the level of the transformer so that the conduit 18 contains at all times a standing column of inert gas. The ice box may be embedded in the ground or floor if desired. Pipe 18 discharges into the transformer at a point above the liquid level therein. The carbon dioxide gas breathes out from the transformer through a restricted vent pipe 20 which communicates with the bottom of a chamber shown as a relatively capacious standpipe 21. The latter communicates at its top with a cross pipe 22, a downward extension of which discharges into the bottom of an open topped chamber 23. This chamber is normally sealed against inlet of air by the body of heavy gas therein,

but it may be an oil seal, to withstand somewhat heavier pressures, if desired.

The breather chambers 21 and 23 serve as a breather connection to the atmosphere through which the transformer may breathe as the volume of gas therein expands or contracts due to temperature changes, and which serves to prevent the passage of the air back through such connection to the transformer. This type of breather connection is described and claimed in my prior Patent No. 1,641,814 of September 6, 1927.

The weight of the gas in the pipe 18 and chamber 21 serves to provide the desirable low back pressure in the ice chamber. This weight, while super-atmospheric, is preferably very small and never capable of producing ice chamber pressure above the triple point of carbon dioxide. In fact,

a pressure of one inch water gauge will suflice, thereby permitting use of a small and light liquid seal for the cover of the ice chamber.

In order that the final venting of the gas may be accomplished above the roof of the building containing the electrical apparatus, I may run the standpipe 21 up through a hollow column 24 which terminates above the building roof 25 and dispose the final venting chamber 23 above the roof.

In the construction of the insulated ice chamber, I prefer to use such heavy insulation that the rate of evaporation of the ice block or the snow mass will be normally slightly less than the rate required. Evaporation is speeded up by the provision of an electrical heating coil 26 in the ice chamber, this heating coil being in circuit with a rheostat 2'7 controlled from any remote controlling mechanism such, for instance, as a gas analyzer, thermostat, barometer, flow meter or other controller, depending upon the exact purpose for which the gas is to be used. By varying the current applied to this heater, the rate of flow of carbon dioxide may be controlled to a nicety without valves or closures.

As one suitable means for controlling the heating coil 26, I have illustrated diagrammatically a circuit-closing thermostat 28 in or at the transformer. This thermostat may be arranged to close the heating circuit upon the fall in temperature, which is occasioned when the load is taken off the transformer or the load is reduced, under which conditions the transformer tends to inbreathe through the vent pipe 20 and breather chambers 21 and 23. The additional gas thus evaporated by the heat supply counteracts the tendency of. the transformer to draw air in through the vent pipe. The thermostat may be arranged to shut off the current after the temperature drop and when the transformer has cooled to normal. While the thermostat is preferably arranged to supply the additional heat only during the falling temperature part of the cycle of use of the transformer, the thermostat can be otherwise arranged to supply the additional heat at another point in the temperature cycle of the transformer.

The control of the current supplied to the heating resistance coil 26 may be secured by any other type of control apparatus known to the art, thus making the operation fully automatic without the complicated mechanical appliances usually required for automatic control of gas flow. For example, an electric carbon dioxide meter or any other type of device which will respond in case the carbon dioxide is diluted with air may be'located at any suitable point in the carbon dioxide gas containing system. Such device will serve to turn on the heating current to the heating coil 26 in case the carbon dioxide becomes too diluted. Such a device will operate only while the dilute condition exists and will shut off the current after the additional heat has supplied enough carbon dioxide to bring the carbon dioxide concentration back to normal.

It will be evident that a similar apparatus can be used for maintaining a predetermined percentage of CO2 in-the holds of vessels in food storage spaces, many other place where automatic control of CO2 percentage is desired.

The resistance may be connected to any other type of control device known to the art, for example, I propose to use it for city water supply carbonation in connection with a flow meter in the water line. The water flow meter can vary the current in the heater in proportion to the rate of flow of the water, thus automatically maintaining a constant proportion of carbon dioxide to water.

In operation the inner container 15 is charged through the top with a suitable quantity of frozen carbon dioxide and then closed by the outer cover 11 with partitioning wall 16, as shown. Evaporation of the frozen carbon dioxide will be quite rapid for a short period of time and the out-breathing of gas will be similarly rapid. As soon, however, as a thermal equilibrium is established, the gas will breathe very slowly outward through the transformer at an evaporation rate initially predetermined by insulation and subsequently varied by the amount of current allowed to flow through the heater and this can be regulated with the greatest accuracy.

Pressures in all parts of the system are low and even a sudden chilling of the transformer can only result in sucking back a certain amount of carbon dioxide, and never in the entrance of contaminating air. Moreover, such sudden chilling is preferably accompanied by a corresponding thermostatically controlled increase in current through the heating resistance which results in a speeding up of gas flow from the ice chamber into the transformer and rapid re-establishment of normal gas volume and pressure conditions in the system.

In the foregoing description, I have referred in some instances to carbon dioxide ice, but my intent is to include loose or compacted snow as well as; blocks produced by direct freezing liquid carbon dioxide.

While I have specifically illustrated and described the preferred embodiment of my invention, it is to be understood that the invention is not, limited thereto but may be otherwise embodied and practiced within the scope of the following claims.

I claim:

1. A method of maintaining a supply of carbon dioxide gas to oil insulated electrical apparatus which includes heat insulating and protecting from access-of air, a quantity of frozen carbon dioxide, permitting the carbon dioxide gas as it evaporates from said frozen carbon dioxide to flow through a valveless conduit delivering said gas in protective relation to the oil in said ap paratus, and regulating the rate of gas production by generating heat in heat transfer relation to saidfrozen carbon dioxide.

2. A method of supplying carbon dioxide gas for industrial purposes, which includes utilizing frozen carbon dioxide as a gas generating source, passing the carbon dioxide gas which evaporates from said frozen mass through a valveless ope conduit to the apparatus to be supplied, and regulating the rate of evaporation of the frozen carbon dioxide by and in accordance with the quantity of gas required in the region of use of the gas.

3. A method of supplying carbon dioxide gaswhich includes the steps of over-insulating a quantity of frozen carbon dioxide and passing the carbon dioxide gas which evaporates from said frozen mass through a valveless open conduit to the apparatus to be supplied, regulating the rate of evaporation of the frozen carbon dioxide by a heater enclosed within the insulation, and controlling said heater from the region of use of the gas.

4. A method of controllably supplying carbon dioxide gas, which method includes utilizing. frozen carbon dioxide as the source of the gas by protecting it against access of air and heat insulating it to reduce its evaporation rate sufficiently to produce only the minimum amount of gas desired, controllably evaporating the same at a higher rate to produce greater amounts of gas and passing the same through a valveless open conduit to the region of use of the gas, in accordance with varying requirements.

5. A method of controllably supplying carbon dioxide gas, which method includes utilizing frozen carbon dioxide as the source of the gas by protecting it against access of air and heat insulating it to reduce its evaporation rate sufficiently to produce only the minimum amount of gas desired, controllably evaporating the same at a higher rate to produce greater amounts of gas and passing the same through a valveless open conduit to the region of use of the gas, evaporation being controlled from such region in accordance with varying requirements by generating heat in heat transferring relation to said frozen carbon 115 dioxide.

6. A method of controllably supplying carbon dioxide gas, which method includes utilizing frozen carbon dioxide as the source of the gas by protecting it against access of air and heat insulat- 120 ing it to reduce its evaporation rate sufliciently to produce only the minimum amount of gas desired, "and controllably evaporating the same at a higher rate to produce greater amounts of gas, in accordance with varying requirements by passing an electric current through an ohmic resistance in heat transferrelation to the frozen carbon dioxide. I

'7. A method of controllably supplying carbon dioxide gas, which method includes utilizing 130 frozen carbon dioxide as the source of the gas by protecting it against access of air and heat insulating it to reduce its evaporation rate sufficiently to produce only the minimum amount of gas desired, and controllably evaporating the same at a higher rate to produce greater amounts of gas in accordance with varying requirements by passing an electric current through an ohmic resistance in heat transfer relation to the frozen carbon dioxide and regulating the same from the 140 region of use of the gas in accordance with the amount of gas required.

8. Apparatus for supplying carbon dioxide gas which includes a gas tight insulating container adapted to receive aquantity of frozen carbon 145 dioxide, a valveless open conduit passing gas from said container to the apparatus to be supplied, heating means within the container for controlling the rate of evaporation of the frozen carbon dioxide, and means for automatically controlling sage from the gas outlet of said inner container to said high level gas outlet being open.

10. A heat insulated container for frozen carbon dioxide including a removable gas-tight cover and having an unobstructed gas outlet through one of the walls, and a bafile partition in the container providing a tortuous internal passageway through which a gas must pass to the outlet opening and which provides thin layers of outflowing gas between the frozen carbon dioxide and the container walls whereby the frozen carbon dioxide is additionally insulated.

CHARLES L. JONES. 

